Providers of services and goods often interact with customers based on a schedule of appointments or similar scheduling items (e.g. reservations at restaurants, waitlists for salons, etc.). For example, restaurants may take reservations for parties of customers on certain dates and times. In another example, an instructor of a yoga class may have reserved slots for respective customers in each class session. Managing appointments (e.g. creating appointments, updating appointments in response to customer requests or changes in the merchant's schedule) and handling payments from customers to the merchants may represent a significant burden on the merchant. For example, the instructor of the above mentioned yoga class may find tasks such as keeping track of appointment change requests, attendance of his customers to the sessions and replacing customers that cancel by offering the appointment slots of the cancelations to other customers to be difficult.